Summary: <p>More than 40 million Americans have arthritis, and it's the leading cause of disability for people who are 65 and older. Almost everyone over 70 has some form of arthritis, but it can affect much younger people too. <a rel="nofollow" class="guestlink">Dr. Clark Smith</a>, an Assistant Clinical Professor of Rehabilitation and Regenerative Medicine at?Columbia?University Medical Center, explains what causes arthritis and how to treat it.</p>
